I am about to buy an XPS 8700 and am choosing between the AMD Radeon HD 7570 (standard) and the nVidea GeForce GTX 645 ($50 extra). In which applications will I notice the difference between the two cards--running many applications at once, photo editing, gaming, etc.? Also, I want my machine to be as quiet as possible (my old Dimension 4550 and 4600 are annoyingly noisy) and wonder which uses more power and therefore generates more heat, requiring more fan cooling. NVidea's site says the 645 max power usage is 130 watts, which is very high. I can't find the spec on AMD's site for the 7570 but another site says its max is 44 watts. If that's right, I'd guess the 8700 would be quieter with the AMD. Also, do you know if you can turn the discrete graphics card off (using the BIOS or another method) when not doing graphics intensive tasks and just rely on the integrated graphics of the CPU?

Finally, Dell's Environmental Data sheets have much lower noise levels for the XPS 8500 than the 8700 (only the first column, 'sound power' is found on the specs for both models):

hard drive access: 2.56 db vs 4.1

optical drive access: 3.88 v 5.2

idle: 2.53 v 4.0

Not sure why this would be the case, though the max power usage for the 8700 is listed as higher too (122 v 87 watts), though the 8700 uses less at idle (41 v 45 watts)

Any help would be appreciated as I'm hoping to buy the machine today or tomorrow.

Based on technical specification of the video cards that you shared, they should work with your system. However, my personal recommendation would be to go for DDR5 video cards as with a negligible price difference they offer significantly better performance than DDR3. One such example is Here.

@2004_4600

GT 645 is significantly faster than AMD 7570, however, it loses to AMD on noise levels and runs a bit hotter. You may refer to link Here. I was not able to find the exact noise levels of these video cards as these are OEM video cards and very few reviews are available online.

As compared to old Dimension systems XPS desktops are considerably quieter. Based on your usage, my personal suggestion would be to go for XPS 8700 and GT 645 video card as it will offer better performance at comparable noise levels.

Unfortunately, XPS 8700 does not offer any means to turn off the discrete video card. However, I researched and found that there are many third party utilities that you may use to minimize the power consumption by underclocking the video card when not using the graphic intensive applications.

Note : These tools are neither tested nor endorsed by Dell. You may use them at your own discretion.

Thanks Sundeep for the info. I agree with you that it's hard to find reviews for these OEM cards. In fact the comparison you link to is apparently based on a different version of the HD7570--with 1G GDDR3 (which you caution Yan12345 from getting) instead of the GDDR5 that the stock XPS 8700's card comes with. AMD's own spec sheet for the HD7570, which I assume is accurate,

makes the distinction between the two types of memory and says that the one with GDDR5 has a 64 GB/s memory bandwidth instead of 28.8 on the GDDR3 model (which your linked comparison, perhaps incorrectly, cites as 25.6 GB/s). The AMD sheet does not give many of the specs cited in the comparison but I assume the GDDR5 version is superior in many of them, so that a true performance comparison would not as strongly favor the nVidea over the AMD.

I'm not sure that the thermal differences are as big as the comparison states, but it does make sense that the AMD uses less power than the nVidea so I ordered my 8700 with the stock AMD. After I get my computer I am tempted to try removing the AMD card and just rely on the i-7-4770's excellent integrated graphics (I am not considering underclocking the video card--I try to do as little fiddlin as possible) in order to save the AMD's power use and fan noise (am I right to assume it does have its own fan?). Is this ok? If so, will I have to adjust any settings or drivers? I have been told that modern computers sense the presence or absence of a discrete GPU and turn off and on the integrated graphics as needed. Is this your understanding as well?

You may also control the fan speed using ATI Catalyst Control center. You may right click empty area on desktop and select ATI catalyst Control center -> AMD Overdrive and control the fan speeds and GPU clocks. (It may or may not be available on OEM video cards)

Note : Any damage incurred to system due to change in default settings would not be covered under warranty.

Yes, the system automatically disables the integrated GPU whenever a video card is installed in the PCI Express slot of system.

You write that "the system automatically disables the integrated GPU whenever a video card is installed in the PCI Express slot of system." Does it work the opposite way too--if I remove the discrete GPU will the integrated graphics automatically turn on without any need to change any settings or drivers? I think this will be my last question. Thanks for all your help.

Yes, the reverse holds true as well. The integrated GPU is automatically enabled by system when you power on the system without a video card installed in PCI Express slot. However, you might need to install the drivers for integrated GPU (if not installed already).